For centuries, coastal nations have sought control over the oceans near their shores. These countries have also sought the right to control the ocean’s valuable resources as coastal nations have long valued coastal waters with large amounts of fish. Fishing is important for food and trade.

Coastal nations quickly realized that they must control and defend their coastal waters in order to protect their ocean resources. In modern day, countries have established exclusive economic zones, or EEZs. An EEZ gives a coastal nation the sole right to explore and extract all natural resources from the ocean for 200 miles (322 kilometers) off its shores. That nation also has the duty to conserve and responsibly use the ocean resources within its EEZ.

Establishing territorial waters

By the seventeenth century, laws governing the ocean began to develop. The ocean was divided into two categories: territorial waters and the open ocean. Territorial waters are the part of the ocean just off a nation’s coast over which that nation may exercise any right.

The nation in control of the territorial waters may defend those waters from other nations. Only the nation in control of its territorial waters could remove resources from those waters. The open ocean, or high seas, is the expansive, deep part of the ocean. Every nation had the right to travel over the open ocean and remove any resources.

From the seventeenth century until the mid-twentieth century, territorial waters extended for 3 miles (4.8 kilometers) off of a nation’s coastline. There were two main reasons for this 3-mile (4.8-kilometer) limit. First, a nation could not claim an area larger than it could protect. Some scholars theorize that this 3-mile (4.8-kilometer) limit developed because a seventeenth century cannon mounted on land could only fire a cannonball that far. Therefore even nations without a strong navy could easily defend the ocean for 3 miles (4.8 kilometers).

Second, the 3-mile (4.8-kilometer) limit supplied most coastal nations with all of the ocean resources that they needed. Until the twentieth century, the main resources that nations took from the oceans were fish and whales. Usually an abundant supply of fish could be found within 3 miles (4.8 kilometers) of the coast. If a sufficient supply of fish or whales were not within that limit, that nation’s fishermen or whales could easily travel out into the open ocean.

By the mid-twentieth century, new technology allowed fishing vessels to travel thousands of miles and remain at sea for months. This led to overfishing (catching fish at a greater rate than they can breed) and overwhaling in many areas. With fish stocks dwindling, coastal nations sought protection beyond the traditional 3 miles (4.8 kilometers) limit.

Oil and natural gas exploration on the seabed also led many nations to look beyond their territorial waters. New technology allowed nations to extract oil and gas from the seabed. Most of this oil and gas lay under the continental shelf and beyond the 3-mile (4.8 kilometer) limit. In 1945, the United States became the first country to abandon the 3-mile (4.8 kilometer) limit. President Harry S. Truman (1884–1972) declared that the United States had the right to all of the ocean resources that existed on the continental shelf. A continental shelf is a gently sloping, underwater plain that quickly drops off to the deep open ocean sea floor.

Many nations followed the United States’ lead and abandoned the traditional 3-mile (4.8 kilometer) limit. Like the United States, some nations claimed all resources on their continental shelves. Some nations extended their territorial waters to 12 miles (19.3 kilometers), and others claimed a 200-mile (322-kilometer) zone.

United Nations and the Law of the Sea

By the 1960s it was apparent that nations would not give up their claims to additional ocean resources. Demand now outpaced supply for fish, minerals, oil, and gas. The United Nations stepped in to help establish a consistent system of ocean resource management. The United Nations is an international organization of nations established in 1945 designed to promote peace and security.

In 1973 the United Nations held the Third United Nations Conference on the Law of the Sea. The conference aimed to settle issues of navigation rights and dividing the ocean’s resources. In 1982 the conference resulted in the United Nations Convention on the Law of the Sea, which set laws for how nations could use the oceans. Perhaps the most ground-breaking part of the United Nations Convention of the Law of the Sea was its establishment of EEZs.

Some ocean resources lie in the open ocean. Open ocean resources are resources that do not lie within any nation’s EEZ. Resources in the open ocean are considered to belong to every nation. Therefore any nation may extract resources from the open ocean.Occasionally, two nations will have EEZs that overlap. When this occurs, those nations may enter into agreements on sharing the resources within that EEZ, or the United Nations may redraw the lines for those nations’ EEZs.

The Law of the Seas also allows for transit passage of naval ships through the territorial waters of another country. Transit passage means that a naval vessel may pass through the territorial water of another country if the ship does so innocently and quickly. Without the right of transit passage, naval and even merchant ships could be forced to travel thousands of miles (kilometers) as a detour to avoid another country’s territorial waters.

Many nations that claim all of the resources found on their continental shelves opposed the 200-mile (322-kilometer) EEZ limit. The continental shelf extended beyond 200 miles (322 kilometers) from the shore in some places. A compromise was made at the Third United Nations Conference on the Law of the Sea that allowed a nation to extend its EEZ up to 350 miles (563 kilometers) to the edge of its continental shelf.

Exclusive economic zones benefit coastal nations. Most of the ocean’s resources lie on continental shelves and an estimated 87% of undersea oil and gas reserves fall under the EEZ of some nation. Almost all of the world’s fishing grounds also fall within an EEZ, but some nations, including the United States, have not ratified (approved and adopted) the Law of the Sea.

Opponents argue that the Law of the Sea could provide the United Nations with authority over waters that a nation considers in its domain. Nevertheless, the United States in 1983 enacted its own exclusive economic zone proclamation similar to those under the Law of the Sea, establishing a 200-mile (322 kilometer) economic zone in most coastal waters.